Ringing arrangement for multiplex circuits



H. A. AFFEL AND J. DAVIDSON JR. RINGING ARRANGEMENT FOR MULTIPLEX cmcuns.

APPLICATION FILED SEPT.26, 1919.

LQUQ QQZB Patented Jan. 3, 1922,

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INVENORS m/wwwm ATTONEY rrso- STATES PATENT OFFICE.

HERMAN A. OE BROOKLYN, NEW YORK,

CLAIR, NEW JERSEY, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF YORK.

RINGING ARRANGEMENT FOE MULTIPLEX CIRCUITS.

Specification of Letters Patent.

Application flied September 26, 1819. Serial No. 328,586.

To all whom it may concern:

Be it known that we, HERMAN A. AFFEL and Join: DAVIDSON, J r., residing at Brooklyn and Montclair, in the counties of Kings and Essex and States of New York and New T Jersey, respectively, have invented certain Improvements in- Ringing Arrangements for Multiplex Circuits, of which the following is a specification.

This invention relates to multiplex carrier systems employing carrier currents, and more particularly to arrangements whereby ringing or other signaling circuits may be transmitted over the channels of such a system.

One of the features of the invention resides in the provision of a source of ringing current common to a plurality of outgoing carrier channels adapted to' superpose the signals from a plurality of signaling circuits upon a common transmission circuit, said source of ringing current being so arranged that in response to a ringing signal transmitted over any signaling circuit, ring ing current from sald source will be applied to the corres onding outgoing channel.

A further eature of the invention resides in the provision of a system of relays for controlling the transmission of ringing current in either direction at the junction point of a low frequency signaling line and a carrier system, said system of relays including a relay responsive to ringing current transmitted over the signaling circuit, and a second relay transmitted" over the carrier transmission circuit, said ringing responsive relays be,- ing so arranged that when either one is operated the operation of the other will be prevented. i

' These features, together withother features of theinvention which will more fully appear hereinafter may be realized in accordance with the detailed arrangements set forth in the following description and illustrated in the accompanying drawing,

Figure 1 of which illustrates a circuit dia main line or a circuit for the transmlssion of responsive to ringing currentcarrier currents. Common transmitting and receiving circuits TL and RL are associated with the main line ML through a balanced transformer 10. In order that the circuits L and BL may be rendered conjugate so that electrical disturbances in the one will be without effect upon the other, the main line ML is balanced by an artificial line or network MN.

L, designates a low frequency signaling line or circuit, which, in common with a plurality of other lines, is adapted to transmit si nals over the main line ML. In the case illiistrated, the line L, is an ordinary low frequency telephone circuit. The line L, is associated through the transformer 11, with an outgoing carrier transmission channel and an incoming carrier receiving channel RL,. These two channels are rendered substantially conjugate by providing an artificial line or network N, for balancing the line L,. The channels TL, and BL, are associated with the common circuits TL and RL through filters TF' and RF, respectively. Similar channels corresponding to other low frequency signaling circuits may be associated with the circuits TL and RL through filters TF and RF, respectively.

' These filters are preferabl of the broad band type disclosed inthe S. patents of George A. Cam bell, Nos. 1,227,113 and 1,227,114 dated May 22, 1917. Said filters are designed in accordance with the principles of the Campbell patents above referred to, in such a manner that they will transmit bands of frequencies in the neighborhood of the carrier frequency assigned to the channel, the bands being of suflicient width to accommodate the frequency variation due to the modulation of the basic carrier frequency by the signaling frequencies. The bands transmitted by the filters TF', and RF, may in practice be the same. The bands transmltted by other filters, such as TF and RF should be sufficiently remote from the bands transmitted by the filters TF', and RF, to allow for frequency separation between the channels.

The transmittingcllannel TL, includes a modulator M,, a band filter TF, and an amplifier TA,. The modulator M, may be of an well-known type, but is illustrated as a duplex vacuum'tube modulator of the type illustrated and described in the U. S.

Patented J an. 3, 1922.

patent to John R. Carson, No. 1343307, issued June 15, 1920. The modulator is supplied with carrier currents of the frequency assigned to the channel, over a clrcult 12. The arrangement is such that carrier currents are not transmitted by the modulator unless the circuit is unbalanced, due to the application of signaling current thereto.

The filter TF is of the general type d1sclosed in the Campbell patents above referred to and is designed to suppress voice frequencies and pass only carrier frequencies. The amplifier TA may be of any well-known character, but is preferably a duplex vacuum tube amplifier, which, as is well known, provides a minimum degree of distortion at high frequencies and hence is wall adapted for the amplification of carrier currents.

The receiving or incoming channel RL includes a detector or demodulator D,. This demodulator may be of any well-known type, but is preferably a duplex vacuum tube modulator of the general character illustrated and described in the U. S. atent to John R. Carson, No. 1343308, issue June 15, 1920. The duplex demodulator described in the said Carson application operates upon the so-called homodyne method of receiving and consequently is su plied from the circuit13 with oscillations of the carrier frequency assigned to the channel. The oscillations supplied from the circuit 13 react in a well-known manner with the received modulated currents, to .detect the low fre uency signaling currents.

v The channel RL also includes an amplifier RA This amplifier is preferably a vacuum tube amplifier, as illustrated, and serves to amplify the detected signaling currents. The incoming circuit RL also includes a filter RF This filter may likewise be of the general type illustrated in the above mentioned patents to George A. Campbell and is preferably so designed as to transmit a range of frequencies extending from zero u to the hi hest frequency employed in or i ary telep onic transmission.

Since it is generally customary to ring over lines such as L at relatively low frequencies, such for instance as 16 cycles per second, it is desirable that some apparatus should be provided at the junction between the low frequency line and the carrier system, to translate these ringing currents into ringing currents of some higher frequency, which is more suitable for the modulation of carrier currents. It has generally been found that ringing current having a frequency of 133 cycles is adapted for this purpose, although it will be understood that other frequencies may be used, if preferred.

In order to produce the translation in ringing frequency above referred to, .the

line L is provided with a ringing responsive relay 13, which through a slow acting relay 14 controls the relay 15 whereb 133 cycle ringing current from a source S may be appiied to the input circuit of the modulator The ringing source RS may be of any suitable source of ringing current, but is preferably a vacuum tube oscillator of a well known type such as is illustrated in Figure 2. This oscillator should be so arranged that it will supply 133 cycle oscillations to any one of a plurality of channels and consequently its output circuit 16 is provided with parallel connections leading to the several channels so that upon the operation of a relay such'as 15 at any channel, the oscillations from the oscillator will be supplied to such channel.

In order to provide the necessary transla tion when ringingcurrent is transmitted from the line ML to the line L a relay 17 res onsive to, 133 cycle ringing current is bri ged across the incoming channel or circuit RL so that the detected ringing current from the detector D, will actuate said relay. Relay 17, through a slow acting relay 18, controls-relay 19 and 20. Relay 19 controls the application of 16 cycle ringing current to the line L,, while relay 20 opens the circuit of the ringing responsive relay 13 to prevent a false operation of said relay and short'circuits the secondary winding of the transformer 11 to prevent 133 relay 15 is so arranged that when it is oper ated in response to ringing current flowing through the windings of the relay 13 the circuit of relay 17 i held open to prevent the false 0 era tion thereof, The relay 14, which is re eased at the same time, prevents the operation of relays 19 and 20.

Further details of the invention may be understood from a description of the operation which is as follows: Talking currents incoming from the line'L, are transmitted through the transformer 11 to the circuit TL and are impressed upon the modulator M High frequency carrier currents from the circuit 12 are now modulated by the modulator M in accordance with the talking currents and the modulated high freguency currents are transmitted through the lter TF', amplified by the amplifier TA and then transmitted through the filter TF' to the common circuit TL.

' pressed upon the circuit from the circuit RL and rents of the circuit 13, so that 133 cycle ring- These modulated carrier fuequencies, t0": gether with modulated carrier frequencies from other channels simultaneously im- TL, are transmitted throu h the transformer 10 to the main line L. Modulated "carrier currents incoming from the line having the proper frequency, are selected by the filter RF impressed upon the detector D,. As a result of the reaction of the received carrier currents and the unmodulated carrier currents from the circuit 13 in the detector D the low frequency talking currents appear in the output circuit of said detector, and are impressed upon the amplifier RA,. fter being amplified the low frequenc currents are transmitted through the fi ter RF to the main line L,. The filter 22, 23, 24 and the bridged connection through the relay 17, which is tuned to 133 cycles frequencies, are not effective to substantially reduce the transmission of talking currents over the circuit RL Sixteen cycle ringing current incoming from the line L actuates the ringing responsive relay 13 which opens the clrcuit of the slow acting relay 14. Upon the armature of relay 14 falling off, ground is disconnected ,from back contact of relay 18 thereby preventing the false operation of said relays 19 and 24 if relay 18 should release. Ground is also connected to the windings of relay15 which is operated. Relay 15, over its front contacts, a plies ringing current from the oscillator R to the input of the modulator M At its lower contact relay 15 opens the circuit of ringing respon-' slve relay 17 to prevent the false operation of said relay. the source RS applied to the modulator M modulates the carrier current from the source 12 and the modulated carrier currents are then transmitted through the filter TF amplified by the amplifier TA and transmitted through filter' TF',v and over the circuit TL to the main line ML. Carrier frequencies modulated in accordance with ringing current incoming from the line ML are transmitted into the'common circuit RL and are selected by thefilters such as RF F etc., into the receivingv channels. The modulated carriercurrents transmitted through the filter RF are impressed upon the input circuit of the detector D where they. react-with unmodulated carrier curing current is detected in the output circuit ofth'e detector D his rin ing current is amplified by the amplifier A and transmitted through the filter RF',. Owing to the impedence of the filter 21, 22, 23, the 133 cycle ringing currents flow th impedance bridge including the ringing responsive relay 1 thereby actuating said re- Relay 17 opens the circuit of the slow the following claims.

The ringing current fromcuits transmission rough the low naling circuit, a

acting relay 18, which at its upperfback contact completes the circuits of relays 19 and 24. Relay 19 over its front contacts a plies 16 cycle ringin current to the line 1%,, while relay 24 ,comp etes the circuit of relay 20. Relay 20 at its lower contact holds open the circuit of a ringing responsive relay 13 to prevent the false operation thereof and short circuits the secondary winding of the transformer 11 to revent 133 cycle energy from the circuit R J1 from being impressed upon the outgoing channel TL,. Relay 24 is a slow release re ay and is employed in the circuit to keep relay 20 operated sufficiently long after the release of relay 19 to prevent any capacity discharge from the line, due ringing, from operating relay 13 and causing a false signaling. It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated, without de arting from the spirit of the invention as defined in What is claimed is:

1 In a multiplex carrier system, a plurality of signaling circuits, a circuit for the transmission of carrier currents, a pluralityof outgoing carrier channels for simultaneously interconnecting said' signaling circuits with said carrier transmission circuit, a source of ringing current common to said channels, and means responsive to ringing current incoming from any of said signaling circuits to apply rmgmg current from said source to the corresponding outgoing channel.

In a multiplex carrier system, a lurality of signaling circuits, a circuit or the transmission of carrier currents, a plurality of outgoing carrier channels for simultaneously interconnecting said signalin cirwith said carrier transmission circuit, a ringing responsive relay associated with each signaling circuit, a source of ringing current common to said carrier channels, and means responsive to the action of any ing carrier channel.

3. In a multiplex carrier system, a plurality of signaling circuits, a circuit for the of carrier currents, a plurality of outgoing carrier channels for simultaneously interconnecting said signalin ciroscillating source to the In a multiplex carrier system, a sigcircuit for the transmission of carrier currents, outgoing and incoming carrier channels for interconnecting said cir- .cuits, a ringing responsive relay associated rality of signaling circuits, a circuit for the transmission of carrier currents, an outgoing and incoming carrier channel individual to each signaling circuit for interconnecting each signaling circuit with the carrier transmission circult, a source of ringing current common to said outgoing channels, a source of ringing current common to said signaling circuits, a ringing responsive relay associated with each signaling circuit, a ringing relay associated with each incoming channel, means responsive to the operation of any one of said'first mentioned relays for applying ringing current from said first mentioned commonsource to the outgoing carrier channel corresponding to the operated relay, means responsive to the operation of any one of said second mentioned relays for applying ringing current from said second mentioned source to the corresponding signaling circuit, and means whereby when either of the relays associated with a given signaling circuit and its corresponding incoming carrier channel is operated, the operation of the other relay is prevented.

6. In a multiplex carrier system, a signaling circuit, a circuit. for the transmission of carrier currents, outgoing and incoming carrier channels for interconnecting said circuits, a relay associated with said signaling circuit, a relay associated with the incoming carrier channel, means controlled by first mentioned relayfor applying ringing current to the outgoing carrier channel and opening the circuit of said second mentioned relay, and means controlled by said second mentioned relay for applying rin ing current to the signaling circuit and or opening the circuit of said first mentioned relay.

7. In a multiplex carrier'system, a signaling circuit, a circuit for the transmission of carrier currents, an outgoing carrier channel having its input associated with said signaling circuit and its output associated with said carrier transmission circuit, an incoming carrier channel having its input associated with said carrier transmission circuit and its output associated with said signaling circuit, a ringing responsive relay associated said with said signaling circuit, a ringing responsive relay associated with said, incoming channel, a third relay controlled by said first mentioned ringing responsive relay for applying ringing current to the outgoing carrier channel, a fourth relay controlled by said second mentioned ringing responsive relay for applying ringing current to the slgnaling circuit, and means whereby, when said first mentioned ringing responslve relay is operated, said second mentloned ringmg responsive relay and said fourth relay are prevented from operation, and said third relay is operated to apply ringing current to the outgoing channel, and means whereby when said second mentioned ringing responsive relay is operated said first mentioned ringing responsive relay and said third relay are prevented from operation and said fourth relay is actuated to apply ringing current to the signaling circuit.

8. In amultiplex carrier system, a signaling circuit, a circuit for the transmission of carrier currents, an outgoing carrier channel having its input associated with said signaling circuit and its output associated with said carrier transmission circuit, an incoming carrier channel having its input associated with said carrier transmission circuit and its output associated with said signaling circuit, a ringing responsive relay associated with said signaling circuit, a ringing responsive relay associated with said incoming channel, a third relay controlled by said first mentioned ringing responsive rclay for applying ringing current to the outgoing carrier channel, a fourth relay controlled by said second mentioned ringing responsive relay for applying ringing current to the signaling circuit, and means whereby when said first mentioned ringing responsive relay is operated said second mentioned ringing responsive relay and said fourth relay are prevented from operation and said third relay is operated to apply ringing current to the outgoing channel, and means whereby when said second mentioned ringing responsive relay is operated said first mentioned ringing responsive relay and said third relay are prevented from operation, the input'of said outgoing channel is short circuited and said fourth mentioned relay is operated to apply ringing current to said signaling circult.

9. In a multiplex carrier system, a signaling circuit, a circuit for the transmission of carrier currents, outgoing and incoming carrier] channels for interconnecting said circuits, said outgoing channel being associated with said signaling circuit through a balanced transformer and said incoming channel being connected to the midpoint-s of the windings of said transformer, a ringing responsive relay associated with said signaling circuit, a second ringing responsive relay associated with said incoming carrier channel, means responsive to said first mentioned ringing responsive relay to apply ringing current to said outgoing ohannel at a point beyond said balanced transformer and means responsive to the operation of said second mentioned ringing responsive relay for applying ringing current to the signaling circuit at a point in said signaling circuit beyond said balanced trans- 10 former.

In testimony whereof we have signed our names to this specification this 24th day of September, 1919.

HERMAN A. AFFEL. JOHN DAVIDSON, JR. 

